1. Field of the Invention
This invention relates to intentional burning, often called ‘prescribed burning’ for wild-land and wildlife management purposes, and in particular to an apparatus for processing and dispensing incendiary capsules for the purpose of conducting such prescribed burning.
2. Brief a Description of Related Art
Prescribed burning is a common activity that is well recognized to produce many wild-land, environmental, agricultural and wildlife benefits. A variety of methods and devices are employed to do this. One main methodology uses flammable liquid or, flammable sludge, which is ignited as it exits the ignition device. Examples of such devices range from hand held ‘drip torches’ to helicopter slung ‘heli-torches’, or to vehicle-mounted or vehicle-towed devices, often called ‘terra-torches’, which eject ignited fuel under pressure much as does a military-type flamethrower. All flammable liquid methods carry with them certain disadvantages. The first such disadvantage is the obvious potential danger to the personnel who operate these devices. Such danger may arise for instance as an unintended consequence of misdirected flame, or possibly by explosion. Secondly, although such devices are effective for starting fires, they tend to consume a large quantity of fuel relative to both the number of fires they start, and to the total area they burn; consequently the ongoing need to re-fuel these devices, which includes the storage, transportation, and often mixing of fuel, imposes a significant operational challenge in the field. This re-fueling requirement also adds environmental risk and significant expense. Thirdly, there exist several physical limitations regarding the design, construction, and operation of any mechanical device which processes and ignites flammable liquids. Such limitations can be related for instance to the need to avoid fuel or flame leakage, or to mitigate the consequences if such leakage occurs, or to other design restrictions due to the potentially detrimental affect of burning fuel upon the mechanical or electrical components of the device. These are some of the reasons why it is desirable to design and employ an ignition apparatus which processes neither flammable liquid, nor flame itself.
One existing method of igniting prescribed burns which avoids the need to emit ignited liquids is that commonly referred to as ‘delayed ignition’. The most common method of delayed ignition is a machine that processes plastic incendiary capsules. Each plastic capsule is partly filled with an incendiary such as potassium permanganate, and, as the capsule is processed within the machine it is injected with a reactant such as ethylene glycol. As a result, after a delay of about 20-40 seconds, the now-mixed chemicals react with one another to create flame, which then causes the plastic capsule to burn. This burning capsule becomes the source of ignition for whatever ground material is intended to be burnt. The main advantage of delayed ignition is the delay itself. This is what allows for a method, or device, that does not have to process actual flame with all of the difficulties associated with doing so, but rather it processes what can be referred to as a ‘pre-flame’ incendiary capsule. This ‘delayed ignition’ technique is the method employed in the present invention.
It is often desirable to conduct prescribed burning from the air. This is especially true if the terrain is difficult or impossible to traverse by ground, or if the area to be burnt is very large in which case the time required to do so by traditional ground based methods may exceed the time window within which optimal burning conditions (wind speed and direction, temperature, relative humidity, etc.) can be expected to persist. When prescribed burning is conducted from the air, this is usually done by helicopter. This can be done by ‘Heli-torch’ as previously mentioned, or, it is also known to install a ‘delayed-ignition dispenser’ within the cabin of the helicopter. Such a dispenser is capable of producing ‘charged’, or injected spheres, which are dropped by gravity from the aircraft to the ground. There are at least three helicopter-deployed delayed-ignition dispensers currently in use, and at least one ground deployed delayed-ignition device:
One such helicopter device is described in U.S. Pat. No. 7,451,679 (Inventors: R. Stevenson and P. Hanbury, Assignee: Raindance Systems Pty Ltd., hereinafter referred to as “Raindance”). This device is designed to be used in combination with a specific ‘series-connected’ incendiary (separate U.S. Pat. No. 6,877,433) which is a flexible belt comprising a large number of connected incendiaries which are fed into Raindance in a manner similar in general principle to that of an ammunition belt that is fed into a machine gun; each incendiary is in turn injected, then led to a cutter which separates it, then drops it upon the ground. As noted in the patent document one of the main improvements sought by Raindance, in particular by means of its positive feeding system, is the elimination of the jamming problem that is often associated with other prescribed burning devices that process individual spheres fed from a hopper. The manner in which Raindance has overcome this problem however still leaves two disadvantages compared with a device that dispenses spheres. The first is caused by the irregular shape of the resultant incendiary. While the symmetrical aerodynamics of a sphere ensure the predictability of that sphere's path when falling through the air, irregular shapes, especially lightweight irregular shapes, are subject to flutter and to unpredictable flight patterns, and, they are also more subject to becoming hung up in the forest's canopy in cases where it is the forest's undergrowth that is the object of the prescribed burning, whereas a sphere is much more likely to reach the ground. Secondly, the Raindance incendiaries provide less thermal energy for ignition purposes than does the inherently more-dense sphere. This relates directly to the fact that the thermodynamic chemical reaction, although it does produce a short-duration intense flame, is not itself the main useful source of ignition the primary purpose of this reaction is to ignite the outer plastic shell so that the plastic becomes, with its much higher thermal energy and flame duration, the source of ignition for the desired prescribed burning.
There are at least two helicopter deployed delayed-ignition devices in use which do use sphere-shaped incendiaries, and both employ a similar basic methodology. One is the Mark III from Premo Plastics and the other is the Red Dragon from SEI Industries. The Red Dragon is the subject of PCT Patent WO 2008/104061 A1. With both of these devices a quantity of plastic spheres, which have been pre-filled with a set volume of incendiary material are deposited into a hopper. When the device is activated individual spheres are caused, in reaction to a combination of agitation and gravity, to line up within downward sloping groves, or ‘chutes’ which have their exit in a chamber within which individual spheres are injected with a liquid reactant (the Mark III can employ up to four parallel chutes, the Red Dragon has two). To inject each sphere that enters this chamber, it is first forced horizontally onto contact with a hollow needle until the needle pierces the ball's surface, then a valve is opened and reactant is pumped into the sphere, then the valve is closed. Next, the ball is moved horizontally in the opposite direction thus withdrawing the needle from the ball, and finally the ball is maneuvered into alignment with an opening through which it falls towards the ground below. Neither of these devices employ underlying mechanical principles which ensure continual ‘possession’ of each individual sphere during its progress through the machine. Instead, their process is oriented towards the sequential treatment of a collective stream of balls in a manner whereby each ball in series is exposed to a certain motion or treatment as it progresses through the various ‘stations’ within the machine, and as a consequence, once in a while a ball can jam somewhere along the process. Occasionally, this will be a ball which has been injected with reactant but does not exit, in which case a fire will occur within the machine. When this occurs, the operator is directed to activate an emergency water supply. Both the Mark III and the Red Dragon are complex machines in comparison to the present invention, and thus are more difficult to operate and are more difficult to maintain. Also, because of this complexity they are less capable of operating at high cycle speed. High cycle speed is desirable for prescribed burning in mainly two instances, which are: first, when attempting to burn material that is not in readily flammable condition, in which case it is desirable to apply a greater number of incendiaries in order to effect more thorough ignition, and second, whenever aerial ignition is desired to be conducted at higher groundspeeds.
A series of delayed-ignition devices are produced by Field Support Services of Florida. The PyroShot (U.S. Pat. No. 7,275,529) is a spring loaded ‘hand launcher for ground ignition’ which indicates, of course, that it is intended for use by personnel while walking on foot. The same company has also produced an HS model which includes a CO2 tank for the purpose of propelling the charged sphere for a longer distance. Further, the same company, in partnership with another company has recently introduced its Green Dragon product. The Green Dragon also employs pressurized CO2 to launch each sphere over a long distance, and it is apparently normally mounted on an ATV type vehicle as opposed to being used by a person on foot. All three products are intended exclusively for use as a ground, as opposed to aerial, application. A review of the original patent indicates that PyroShot's mechanisms for performing the main basic tasks of (1) feeding a sphere into the machine, (2) injecting reactant into the sphere, and (3) ejecting the sphere from the machine are fully dissimilar to the mechanisms employed in the present invention. For these reasons it would not appear to be necessary to further discuss the PyroShot products in the context of relevant prior art.
The applicant is aware of no other ‘delayed-ignition’ devices in addition to those described above.